As is known, in order to bind sheets arranged in a pack and perforated along a perimeter edge of the pack, binding devices are used having substantially tubular conformation comprising an elongated edge having a substantially C-shaped transversal section and a plurality of curved flexible tabs obtained integrally with the portion of edge and arranged spaced apart from each other to form an elastic structure shaped as a comb. Each of said tabs is adapted to be inserted in a respective hole (preferably rectangular in shape) of the pack to cross the pack and be arranged with the end portion thereof abutting against an inner surface of the edge portion, thus making a stable connection between the sheets which are bound to form a booklet.
The above-described, binding devices of known type have a plurality of drawbacks, including:
the elongated end portion protrudes frontally and laterally from the booklet; for such a reason, it is often difficult to arrange the booklet on a shelf or put it near other bound booklets;
there is a need for binding devices having different dimensions, in particular different size and shape of the elongated edge portion, in order to bind booklets having different thickness;
it is not generally possible to print text and words by means of priming on the bound booklet because such an area is formed by the outer surface of the edge portion which is bent and is made of plastic material; and
the binding device (made of plastic material) is to he separated from the sheets of the pack should there be a need to dispose of the booklet, for example burn it.